Grid for electron discharge devices



Feb. 27, 1951 s. e. CARNE GRID FOR ELECTRON DISCHARGE DEVICES Filed Dec.17, 1948 INVENTOR GERALD G. CARNE Patented Feb. 27, 1951 UNITED STATESTENT ()FFICE Radio Corporation of America, a corporation of DelawareApplication December 17, 1948, Serial No. 65,817

Claims.

The present invention relates to improvements in electron dischargedevices of the gas discharge type, and more particularly to an improvedamount for such devices including an improved 2 to the cost of the grid.Grids of the type referred to have heretofore comprised two parts weldedtogether at two displaced locations. In addition, they have required twoforming opgrid. 5 erations, one for forming each part prior to weld"Some types of electron discharge devices, such ing the parts together,and the other for forming as thyratrons,employacontrol grid made ofsheet the grid after the parts have been welded tometal, the widersurfaces of which are disposed gether. This requires equipment andoperator parallel to the path of electron flow. A sheet time thatappreciably adds to the cost of the demetal type of control grid issuitable for thyra- 1O vice inwhich the grid is used. trons since inmost instances the nature of the It i therefore the object of theinvention to control function is to block electron flow through providean improved mount for an electron disthe device, except when the grid isexcited by a charge device. critical voltage in response to which itpermits Another object is to provide an improved supsuch flow. Thecontrol grid i in most instances port for a grid in the mount of anelectron disinoperable to stop the flow and such stoppage is chargedevice. usually accomplished by circuits external of the Aiurther objectis to provide an improved grid device. A sheet metal type of grid isWell suited structure contributing to good support thereof for this typeof control. in an electron discharge device and to good op- One of theproblems presented by this type of eration of said device. grid involvesthe requirement that the grid orig- An additional object of theinvention is to proinally during manufacture of a device be criticalvidean improved sheet metal grid of relatively 1y spaced from otherelectrodes of the device for simple structure lending itself to goodsupport performing its critical control of the initiation of in anelectron discharge device and resulting in electron flow therein, andthat this spacing and economies in the manufacture of the device. theform of the grid be maintained without Another object is to provide aone-piece sheet change during useful life of the device. metal gridrequiring only one forming operation. Another problem concerns themanner of sup- A further object is to provide a one-piece sheet port ofthe grid in an electron discharge device. metal grid adapted to besupported in such a man- Where the grid is made of sheet metal it isdesirnor that its form is preserved against distortion able that alllegs or elements thereof be directduring operation of a device in whichit is emly supported on relatively rigid support struc-- ployed. tures.Sheet metal grids heretofore employed in Another object is to provide aone-piece sheet thyratrons have included elements that depend metal gridthat contribute to effective support for their support on other elementsof the grid. thereof against displacement with respect to other Thistype of support weakens the grid structure, electrodes in a device andagainst deformation particularly since the elements thereof serving orcollapse in response to thermal operating conthe dual function of theactive portion of the grid ditions of the device in which it is used. asWell as support means, may be weakened dur- A further object is toprovide an improved ing use so as to distort an active portion of themount including a one-piece grid and supports grid out of its originallyand critically adjusted therefor wherein the supports and the gridstrucposition, thereby rendering the device unsuited ture cooperate tosupport the grid elements for fine control purposes. againstdisplacement with respect to each other The manner of support of a gridcan also give and with respect to other electrodes of a device rise toanother problem. For example, one type in which it is used. of'gridheretofore used and designed for support Another object is to provide asheet metal grid between two spacer plates, is provided with bearandsupport therefor that contributes to ease in ing surfaces engaging innerfaces of said plates; mounting the grid in an electron discharge doWhere the spacer plates are fixed against relative vice. movement withrespect to each other, expansion Further objects and advantages willbecome eviof the grid in response to heat resulting from cer- ,dent asthe description continues. tain operation conditions may cause the gridto Referring now to the drawing: collapse or become distorted and thismay con- Figure 1 shows a longitudinal section along tribute to faultyoperation of the device in which lines l-l of Fig. 2, of a thyratrontype of electron it is used. dischargedevice in which my novel grid maybe A further problem is encountered in respect used;

Figure 2 represents a cross-section along the lines 22 of Figure 1 andindicates the crosssectional structure of the device shown in Figure las well as a portion of my novel grid;

Figure 3 is a cross-section of the mount along the lines 3-3 of Figure 2and shows one side edge and the general U-shape form of my novel gridand the manner in which it is supported by the insulating spacer platesof the device;

Figure 4 is a top view of Figure 3 and shows the upper end of the mountand the manner in which my novel grid is supported at the upper endthereof;

Figure 5 is a perspective view of my novel grid after it has beensubjected to the one forming operation required in accordance with theinvention; and

Figure 6 is a perspective view of a prior art sheet metal grid includingtwo parts welded together at two locations and requiring two formingoperations, and provided with bearing surfaces engaging the inner facesof two spacer members.

Considering the drawing in more detail, there is shown in Figure 1 athyratron type of electron discharge device in which my novel grid maybe used. The device includes an envelope iii closed at one end by aheader or base H having contact prongs I2. The envelope contains asuitable gas permitting a discharge therethrough and an electrode mountincluding a screen grid I3, having beam forming members I4, shown bestin Figure 2, a cathode 15, a plate l6 and a sheet metal control grid llsupported between a pair of substantially parallel axially displacedinsulating spacer members or plates l8 and 19. The grid H is supportedin the device in such a manner that its flat surfaces lie in planesparallel to the direction of electron flow in the device duringdischarge therethrough.

According to the invention, my novel sheet metal grid I! comprises aone-piece structure, shown best in Figure 4, having legs 23 and 2| andtransverse portion 22. Leg may be longer than leg 2| for a purpose to bedescribed.

Further, according to my invention the insulating spacer members I8 and19 are provided with slots 23, 24, and 26 for receiving the legs 2c, 2!.When assembled in an electron discharge device, as shown in Figures 3and 4, the legs 29 and 2! of my novel grid extend through the slots 23and 23 in the upper spacer member 18, with the transverse portion 22bearing against the upper face of this spacer member. The lower portionsof the legs extend through slots 25 and 28 in the lower spacer memberl9. Leg 20 may be longer than leg 2i to permit it to extend fartherbeyond the lower face of the lower spacer member for convenience inconnection to a lead-in.

The slots 23, 24, 25 and 26 in the upper and lower spacer members 18 andH! are dimensioned to receive the grid legs 20 and 2| in a snug fit. Theslots in each of the spacer members are critically spaced from eachother so as to receive the legs 2% and 2i of my novel grid withoutdistorting its U-shaped form or disturbing the critical predeterminedspacing between the legs required for a sharp response to apredetermined voltage excitation of the device in which it is used. Theslots referred to, in the spacer members [3 and 19 therefore properlylocated my grid in the mount of a device in which it is used and serveto restrain the grid from displacement out of its properly locatedposition.

This restraint against displacement of my grid is mainly accomplished asthe result of the snug support provided at each end of the legs 20 and21 thereof by the snug engagement therewith of the edges of slots 23,24, 25 and 26. Thus, any transverse displacement of the grid withrespect to the mount is prevented by the snug fit of the legs in theslots referred to. While this snug fit also contributes to a restraintof longitudinal movement of the grid with respect to the mount, suchmovement is in the main prevented by the abutting engagement between thetransverse portion 22 of my grid and the top surface of the upper spacermember [8, and by the connection of a lead-in 21 to leg 20 in a weld 28adjacent the bottom surface of the lower spacer member [9.

The engagement between the transverse portion 22 and the spacer member18 and the engagement between the weld connection 28 and the spacermember l9, effectively prevent longitudinal movement of the grid as awhole with respect to the mount. However, these engagements do notprevent longitudinal movement of portions of the grid legs that might becaused by expansion thereof in response to heat during certain operatingconditions. This is for the reason that such expansion involves movementof longitudinal portions of the grid legs in opposite directionssimultaneously and in directions opposite to that in which theengagements referred to provide restraints.

The freedom of my grid to move longitudinally in the manner indicated inresponse to expansion thereof is an advantageous feature of myinvention. It permits absorption of the expansion of my grid in linearelongation thereof and prevents a buckling or collapse that might occurin the absence of such freedom to move longitudinally. Since as has beenindicated herein the sharpness of control afforded by a sheet metal gridis substantially entirely dependent on its spacing with respect to theelectrodes in a device, a buckling or deformation of portions of thegrid would change their rela-- tive positions in the mount and result ina loss in sharpness of control of the grid. It will further be notedthat longitudinal displacement only of my grid has no adverse effect onthe sharpness of its control function. This is for the reason that mygrid is longitudinally uniform in structure between the spacer membersI8 and 19, which define the portion of the device in which the grid isoperative.

It will be appreciated from the foregoing that my novel grid has manyadvantages over prior art types of sheet metal grids, one of which isshown in Figure 6. The grid shown in Figure 6 is a common form of gridheretofore used in electron discharge devices such as thyratrons. Itincludes two parts 29, 30 which are joined in welds 3!, 32, each partterminating at a location intermediate the other part to provide bearingends 33, 34 for bearing against the inner surfaces of spacer. members,not shown. This grid is objctionable in that it requires two formingsteps, one for forming each of the members 29, 39 prior to joining them,and the other for forming the grid structure after the members thereofhave been welded together. And additional objection to this grid residesin the fact that the bearing end surfaces 33, 34 prevent longitudinaldisplacement of portions of the grid in response to expansion thereof,with the result that such an expansion is permitted to find an outlet ina buckling or other form of distortion or collapse of the grid.

In making my novel grid there is first stamped from sheet metal stock arectangular form having a predetermined width and length required for aparticular grid. This rectangular form is then bent by a tool, notshown, to provide a U-shaped form shown in Figure 5. This formingoperation is accurately performed and no further forming action isnecessary. The mounting operation involves threading the legs of my gridthrough the slots previously referred to in the spacing members l8 and l9. If during the manual handling of the grid after its formation andprior to its insertion in the slots referred to, the legs thereof shouldbe disposed out of true parallel relation, such deforming of the gridlegs is corrected by the novel feature of my invention residing in thecritical spacing of the slots in each of the spacer plates referred to,and the snug fit of the legs in said slots. According to my invention,therefore, any inaccuracy in the spacing between the legs of my gridresulting from handling is effectively corrected and the correct spacingpreserved during the life of the device in which my grid is used.

After the grid is threaded into the slots referred to the longer leg maybe connected to a lead-in as described above.

The fabrication of my novel grid and its assembly in a mount are,therefore, characterized by simplicity and economy. In addition to beingeasily and economically made and mounted, my grid is also superior toprior art grids in operation and contributes substantially to the goodfunctioning of a device in which it is employed.

Various modifications may be made in my novel grid and in the manner ofits support in an electron discharge device without departing from thespirit of the invention which I desire to be given a scope commensuratewith the appended claims.

What I claim is:

1. A mount for an electron discharge device includin spaced insulatingspacer member and a grid disposed between said members, said gridcomprisin a U-shaped structure made ofsheet metal having parallel legslying in parallel spaced planes and a transverse portion, said spacermembers each having two parallel and coextensive slots spaced from eachother by a distance equal to the length of said transverse portion forsnugly receiving said legs with said transverse portion abutting againstone face of one of said spacer members, and the free ends of said legsextending beyond the remote face of the other of said spacer members,whereby said grid is free to expand longitudinally without disturbingelectrode spacings in said device.

2. A mount for an electron discharge device including axially displacedinsulating spacer members and a grid disposed between said members, saidgrid comprising a U-shaped structure made of sheet metal having parallellegs lying in parallel planes and a transverse portion, said spacermembers each having two coextensive slots spaced from each other by a,distance equal to the length of said transverse portion for snuglyreceiving said legs with said transverse portion abuttin against oneface of one of said spacer members, the free ends of said legs extendingbeyond the remote face of the other of said spacer members, and alead-in connected to one of said legs adjacent said remote face of saidother of said spacer members, whereby said grid is restrained againsttransverse bodily movement with respect to said spacer members, but ispermitted to expand longitudinally in response to thermal expansionwithout disturbing its space relationship with respect to otherelectrodes in said device.

3. A mount for an electron discharge device including two parallelaxially displaced spacer members and electrodes mounted between saidmembers, said electrodes including a cathode, an anode and a griddisposed between said cathode and anode, said grid being made of sheetmetal and including two straight legs lying in two parallel planes andextending from one of said spacer members to the other, the planes ofsaid legs also being parallel to a plane including said cathode and saidanode, whereby the edges of said legs are normal to the path of electronflow from said cathode to said anode, said spacer members havingcoextensive slots for receiving end portions of said legs in snug fits,said grid having a transverse portion connecting adjacent ends of thelegs at one end of said grid and abuttingly engagin the outer face ofone of said members, whereby said grid is securely supported by saidspacer members against lateral movement but is free to movelongitudinally in response to thermal expansion thereof withoutdisturbing electrode spacings in said device.

4. A mount for an electron discharge device including two spacedflatspacer members and electrodes disposed between the inner faces ofsaid members, said electrodes including a onepiece sheet metal gridhaving two legs, said spacer members having coextensive slots disposedin critical space relationships with respect to each other, and withrespect to others of said electrodes for receiving end portions of saidlegs in snug fits, whereby said grid is properly positioned in saidmount on engagement of said end portions of the legs thereof by saidslots and free to move longitudinally without disturbing spacedrelations of elements of said device.

5. A mount for an electron discharge device including two axiallydisplaced parallel spacer plates and electrodes disposed between theinner faces of said plates, said electrodes including a sheet metal gridhaving two flat and straight parallel legs and a flat transverse portionconnecting two adjacent ends of said legs, said plates having slotsreceiving the ends of said legs, a flat surface of said transverseportion engaging the outer face of one of said plates, the free ends ofsaid legs extending through the slots in the other of said plates andbeyond the outer face thereof, and a lead-in welded to one of said legs,said lead-in engaging said outer face of said other of said plateswhereby said grid is supported against bodily longitudinal movementwhile capable of sectional longitudinal movement in response to thermalexpansion thereof without disturbing the space relation of said gridwith respect to others of said electrodes disposed between said plates.

GERALD GLEN CARNE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,694,189 Ruben Dec. 4, 19282,248,987 Green July 15, 1941

